Testosterone propionate produced no stimulating effects on spermatogenesis in the adult [male] starling. Testes naturally in the later stages of spermatogenesis were unaffected by the androgen. Testes naturally in early spermatogenesis showed an initial depression in size and activity. This was more marked in birds on "short-days" than in starlings treated with daily light rations which are otherwise stimulating to spermatogenesis. Under continued treatment with light and androgen, spermatogenesis occurred, but less slowly than without androgen. The cessation of spermatogenesis which normally occurs at the end of the breeding season does not appear to be produced by an androgen qualitatively like testosterone propionate.